多物理量融合之即時碾壓土壤含水量與密度量測技術研發( II )

Abstract

碾壓土壤結構物與民生安全息息相關，此類建築物於營建時之含水量與密度控制品管不當常造成 填方塌陷、堤防淘空及擋土結構破壞等危害民生之情事，而有造成人民生命安全及財產損失之虞，因 此重量含水量與乾密度是為碾壓土壤營建過程中極重要之品管指標。目前國內外普遍使用之直接量測 與核子量測技術分別有耗時、檢查點可能無法具完全代表性以及輻射污染與人員訓練及器材管理程序 繁瑣之困擾，因此近幾年國際上積極發展可取代核子方法的儀器。目前尚無任一單一量測技術能達到 取代核子量測技術的水準，但電磁波時域反射（Time Domain Reflectometry, TDR）法經評估極具潛 力，且可再結合彈性波量測技術以及熱導性質量測技術提供額外資訊，本研究之目的即在於發展結合 多物理量之非核子式土壤含水量與密度量測技術。碾壓土壤各種物理特性之行為極為複雜，不僅是土 壤含水量與密度之函數，各技術因未能有效考慮重要的影響因子而無法達到取代核子式儀器的水準， 本研發工作於第一年度首先透測基礎地探討碾壓土壤各項物理量（介電頻譜性質、導電率、剪力波速 性質以及熱導係數性質）之行為，並透過貝式分析法提出具可行性之多物理量融合之即時碾壓土壤含 水量與密度量測方法，本年度預計繼續完成第一年度之物理量行為探討，並進一步設計具量測準確 度、施作效率性及操作便利性的現地量測系統，進行現地實測與評估。

The quality control of compacted soils relies on measuring the moisture content and dry density of soils during compaction, which determine the strength and hydraulic conductivity of earth dams, road embankment and retaining structures. Inappropriate moisture content or insufficient dry density during construction would cause excessive ground settlement and failure of earth structures. Conventional quality control methods are time consuming and the nuclear method although efficient is potentially hazardous. Due to increased regulatory restrictions and growing concerns over the safety of using a device with a nuclear source, there is an increased effort to find a possible alternative to the nuclear gauge for compaction control. The replacement device must accurately assess the properties of the compacted fill and do so in a timely manner that does not impact construction. Up to date, no single measurement technique is successful in meeting these goals. However, Time Domain Reflectometry (TDR, measuring the electrical property of compacted soils) is ranked as the most potential technique, which may be further complemented by seismic wave velocity or thermal conductivity measurements. The objective of this research is to develop an integrated measurement technique for rapid determination of soil water content and dry density based on fusion of various non-nuclear physical measurements. The behavior of various physical properties in compacted soils is more complicated than just a function of two main factors (dry density and water content). The lack of the knowledge in considering major influencing factors is a main problem. Electrical, thermal, and elastic wave behavior of compacted soils were thoroughly and fundamentally investigated in first year, based on which a multi-physical data fusion approach, Bayesian Inference, was proposed for rapidly determining soil water content and dry density. In the second year, the experimental studies will be finished and a reliable, efficiency, and workable in-situ multi-physical measuring system will be designed and evaluated with field experiments.